1. FIELD OF THE INVENTION
The invention relates to an annulus safety valve for use in a subterranean oil and/or gas well and to a method of controlling pressure within an annular area using the safety valve.
2. BRIEF DESCRIPTION OF THE PRIOR ART
Subsequent to the drilling of a subterranean oil and/or gas well, it is completed for the production of fluid hydrocarbons therein by introducing into the well, on a production or workstring, a well packer through which is secured the production or workstring extending to the top of the well. The well packer will be sealingly engaged with the interior of the casing in the well and somewhat above a production zone through which the produced hydrocarbons initially flow interior of the casing, thence through the interior of the packer and production or workstring to the top of the well. Sometimes the packer is included as an integral component of a more complex tool, such as a tubing hanger or the like. Such tools may be run and set in the well together with other tools on the production or workstring in one trip of tubing within the well, or may be run and set separately.
It often occurs in a well that a plurality of zones are intended to be produced either concurrently or selectively. It also occurs that the well "annulus", i.e., that area in the well defined from the inner diameter of the well casing to the exterior diameter of the production and/or workstring, is utilized to either produce fluid hydrocarbons from another production zone either above or below the first zone, as described above, or for purposes of injecting treatment fluids from the top of the well to a particular zone.
Just as safety valves must be provided to selectively sealingly block the interior of the production or workstring so that flow of fluid hydrocarbons from the production zone to the top of the well may be shut off at such safety valve to prevent a "blow out" in the event of an uncontrollable situation, such as a fire, or the like, so the well "annulus" must likewise be controlled if it is exposed to a second production zone or is to be used for injection of fluid for one reason or another from the top of the well to a given production zone within the well.
While annulus safety valves have been utilized in the art, none are "full opening", i.e., the internal diameter of such safety valve components for the annulus is not substantially equal to the internal diameter of the production or workstring, such that tools carried on remedial coiled tubing, wire or electric line, may safely and completely pass therethrough without any interference to longitudinal and/or rotational movement.
As set forth above, the purpose of such annulus safety valves herebefore utilized has been to control well pressure below such valves from communicating the tubing/casing annulus across such valves. It would be desirable to provide control of the annulus, yet permit selective injection of chemical inhibitor, kill fluid, and the like within the tubing casing annular area from above the annulus safety valve to the area therebelow and within the interior of the casing on a selective volumetric basis.
Furthermore, it would be desirable to permit increased fluid flow across such annulus safety valve, selectively, merely by increase of fluid pressure within the tubing casing annulus above the annulus safety valve by permitting plug means which may be shearingly removed from sealing engagement within the valve to permit increase in fluid flow therethrough, such plug means also being replaceable by additional valve head and seat members of the same design and operation as other valve head and seat members forming the annulus safety valve.
The present invention addresses the above-identified problems and provides a unique annulus safety valve as described below and in the drawings incorporated herein.